Constant-frequency generator



Aug. 23, 1932. F. CONRAD CONSTANT FREQUENCY GENERATOR Original FiledJan, 18, 1929 2 Sheets-Sheet Aug. 23, 1932.4 F, CONRAD 1,872,896

CONSTANT FREQUENCY GENERATOR Original Filed Jan. 18, 19,29 n 2Sheets-Sheet 2 www l lil-.Ila f4 lc la 2o Sethd /oaoa mu-1 Currenf 80 BY76 8/ 77 7 TTORNEY a constant-frequency-generator Patented Aug. 23,1932,

1,872,8img

FRANK CONRAD, .orjPENN TowNSHIP. ALLEGHENY COUNTY, PENNsYL'vAN'iA, .as-

SIGNOR TO WESTINGHOUSE ELECTRIC MANUFACTURING COMPANY, A CORPORA- TION FPENNSYLVANIA CONSTANTFREQUENCY GENERATOR 1930. Serial This applicationis a division of my applifation, Serial No. 333,374, filed January 18,1929.

My invention relates to high frequency generators of the tuning-fork orvibrating-reed type.

The object of my invention is to provide means for maintaining theyfrequency of a generator of the above-mentioned type` oonstant. p

In practicing my invention, I em loy a tuning fork which is mounted in ab ook of metal and driven by electromagnetic means; The frequency ofvibration of the tuning fork is maintained constant by periodicallyheating the tuning fork by an amount that is dependent upon t-hedeparture of the vibrations from the desired fre uency. The heat isapplied periodically to t e'tun'ing fork by means of a heater elementwhich is 1n contact wlth the metal block and is connected to a systemincluding an electric clock and a synchronous motor, as Will be morefully described hereinafter.

Other features and advantages of my invention will appear from theyfollowing description, taken in connection with the accompanyingdrawings, in which, s

Figure 1 is a diagrammatic -view'of the apparatus and electricalconnections employed in my constant-frequency generator; i

Fig. 2 is a diagram to aid in describing the operation of myconstant-frequency generator:

Fig. 3 is a diagrammatic view of the -heating box and heating apparatusfor the constant-frequency-generator tuning fork;

Fig. 4 is an end elevational view ofthe tuning fork and its holder anddriving mechanism, and l v Fig. 5 is asectional view, taken along theline V-V of Fig. 4. i

Referring to the drawings, the portion o f system, indicated in Fig. 1by the legend heater yand Vfork, is shown schematically in Fi 3. Thisportion of the system .comprises al eat-insulated boX 67 within whichare locatedr two electric heaters 68 and' 69. The uppery heater 68 isconnected to a source of 'current' through Original application tiledJanuary 18,r i929, Serial No. 333,374. Divided and this applicationiiledMarch',

a thermostatic relay 70 of the bimetallic type,

A condenser 7l is shunted across the relay contacts to reduce sparking.The interior of the heater box is maintained at a substantially constanttemperature by means of the heatv yer 68 and the thermostatic relay 70.The

f tors and v7 6, respectively, arey electromagnetic devices for drivinglthe tuninfr fork.

The construction of the tuning-flink holder 7 2, the tuning` fork,andthe electromagnetic driving means `73 and 74 can best vbe understoodby referring to Figs. 4 and 5. The holder 72 comprises two solidmetallic blocks 77 and 78,- preferably of brass, each v having avertical hole 79 drilled off center, therein. Each block has a largerthreaded hole, drilled at right-angles to the vertical hole 79 andcommunicating with` it, in which one of the electromagnetic drivingunits 73 and 74 is supported. The two blocks 77 and 78 are clampedtogether by means of bolts 80, with their thin walls adjacent to `eachother and .with a sheet yof magnetic material 81 between them. In thisWay, two well portions 79 are formed, separated by a thin partition ofmagnetic material 81 and nonmagnetic material 82. A square notch 83 iscuty in the middle of the upper edge of the partition. by means of bolts85, between two solid metal blocks 86 and 87, preferably of brass.Blocks 86 and v87 are secured, by bolts 88, to the blocks 77 and 78 insuch position that a portion of the tuning fork 84 is located within thenotch 83 cut in the partition, While the prongs 99 are located withinthe wells 79. A clip 10() is attached at the top of the block forholding a thermometer 101.` n

The tuning-fork-driving elements 73 and 74 comprise telephone-receiverunits having pole pieces adjacent to the prongs 99 of the tuning fork84. The pole pieces are soft- `iron pieces attached to the'poles of apermanentr magnet 102. .They have coilsnl03y The tuning fork 84 isclamped,

. the forli heater 69. y

,plied to the fork 84 is controlled by means of asynchronous motor 108(preferably of the mounted thereon which are connected to the bindingposts 104. The driving elements are held in place by means of set screws105.

The partition above-specified is provided for electrically shielding thedriving elements 73 and 7 l from each other.

Since the tuning forl 84 is in contact with the brass blocks 86 and S7,which are good heat conductors, the temperature of the forli 84 may becontrolled by varying the amount of heat applied to these blocks. Thisis done by setting the fork holder72upon an electric heater 60, as shownin Fig. 3, and by controlling the amount of current flowing through theheater by means of the circuit shown in Fig. 1. VReferring to'Fig. 1,the constant-frequency current is generated by so connecting theforlvdriying elements 73 and 7 4 to an amplilier 106 that the fork 34 isvibrated at its natural frequency. In the example being described, a500G-cycle current is generated. rlhe driving element l. is connected tothe input of the amplifier 100 by conductors 6, while the drivingelement 7 3 is connected to .the output of the amplifier 106 byconductors from the Vamplifier output.

The frequency of the current generated is controlled by varying theamount of heat supplied through the heater circuit 107 to The amount ofheat supphonic-wheel type.) connected to the forkainplifier outputthrough an amplifier 109,

and byr means of an electric clock 110.

When a current ofthe desired frequency is being generated, thesynchronous motor 10S connects the forlcheater circuit 107 to a sourceof. current at regular intervals, while It-heelectric clock 110disconnects the heater circuit 107 from the source at like intervals.

In this way, the fork heater 60 is alternately connected to, anddisconnected from, the source of current, which. 1n the exampleillustrated, is a 110-volt alternating-current supply. p l,

',The circuit connecting the current supply tothe forli heater 69 may betraced from one dicator lamp 117 and resistance 118, in parallel, aconductor 119, one conductor of line 107, the forl heater 69, the otherconductor of'line107 and the conductor 120, back to the rother terminalof the alternating-current supply. The winding of relayV 114, whichpulls upthe armature 113 an'd'thereby con- 'nects the fork heater 69 tothe alternating:

current supply, has one terminal connected to ground and the otherterminal connected, through a resistance 121 and a conductor 122, to oneterminal of a battery 23, the other lterminal of the battery 123 heiligconnected armature'113 of the relay 114C is pulled up to connect thefork heater 69 to the 110 volt supply. Vhen the armature 125 of thepolar relay 1241- rests against the right-hand contact, the Winding ofthe relay 11-l is short circuited, and the armature 113 drops down, thusdisconnecting the fork heater 69 from the 110 volt supply.

The armature 125 of the polar relay 124 is pulled over to the left, toconnect the fork heater 69 to the 110 volt supply, each time the upperterminalrof the left-hand windin g 127 of said relay is connected toground by means of the synchronous motor 108 through the conductor 128,brush 120, contact elei ent 130, shaft 131, ring 132 and brush 133. Vleshaft 131 is connected tothe synchronous rootor 103 through a gearreduction unit so that contact between element 130 and brush 129 is madeonce every two seconds if the tuning fork 8l. is vibrating at the properfrequency.

The polar relay armature 12o pulled against the right-hand contact, todisconnect the fork heaterf69 from the 110-volt supply, each time theelectric clock 110 pulls the armature 134 of the polar relay 135 againstthe left-hand contact. Since the electric clock 110 actuates the polarrelay 135 at regular intervals, (once every two seconds, in the exampleillustrated) the forli heater 69 will be disconnected from the 110-voltsupply at like intervals. The synchronous motor 103 and the electricclock 110 are so adjusted with respect to each other that theyalternately conneet and disconnect the fork heater' 69 and the currentsupply. The electric clock 110 preferably, of the type described an dclaimed in my copending application. Serial No. 176,061, liled'March 17,1927, in which the pendulum is driven by charging and discharging acondenser through a driving coil. The'coil of the polar relay 135 isconnected in series with this driving coil.

When the armature 13a is pulled against the left-hand contact. a circuitis completed Afrom a battery 136, through a resistance 137,

a conductor138, a relay winding 139, a conductor 140, the relay armaturelil-lf and the left-hand contact, back to the battery 136. This pullsthe relay armature 141 against the upper contact and connects the upperterminal of the right-hand winding 14.2 of the polar relay 124 to groundthrough conductor 5Lavasee 143 and armature 141. The" armature 125'ofthe polar relay 124 is then pulled 'against the right-hand contact, andrelay armature 113 drops, 'thereby disconnecting the heater 69 from thecurrent supply. i

A special circuit is provided for passing current through thepolar-relay windings 127 and 142 in response. to they closing of eitherthe synchronous motor or the electric-clock contacts. The circuitcomprises the battery 123 which is connected, throuo'h aconductor 144, aresistance 145 of a fewtliundred ohms anda second resistance 146 ofseveral me ohms, to one terminal of a condenser 14 The other terminal ofthe condenser 147 is connected to the other terminal of the battery 123through ground. A circuitis likewise completed from one terminal of thebattery 123, through the conductor 144, the resistance 145, a secondresistance 148 similar to resistance 146, a condenser 149 similar tocondenser 147 and, through ground, to the other termi-` nal of thebattery 123. e

By means of the circuit described above,

. the condensers 147 and 149 are kept charged.

Accordingly, when the upper terminal yof either polar-relay winding 127lor winding 142 is connected to ground, by means of the synchronous motor108 or the electric clock 110, the condenser to which the windinr isconnected discharges through that winding. This momentary yflow ofcurrent through the winding is suiicient to pull the armature 125against a contact. Because of this arrangement, the 4armature 125 of thepolar relay 124 may be pulled away from a contact very shortly after itis pulled against it, since the rush of currents lasts a very shorttime.

I Therefore, the armature 125 of the relay may fio CIS

be pulled away from a relay contact even though the contacts of thesynchronous motor 108 or those of electric clock 110, which pull thearmature 125 against the relay contact, are still closed.

The condensers 150 and resistances 151 are employed` to reduce sparkingat the relay contacts. 2 y f The following values of capacity,resistance and voltage have been found satisfactory although, obviously,other values may be employed, if desiredzkresistances 146 and 148 equal5 megohms; resistance 145 equals 1000 ohms; resistance 112 equals 50ohms resistance 116 equals 800 ohms; resistance 118 equals ohms;condensers 147 and 149 equal .25 micro-farads; resistance 121 equals10,000 ohms; and the voltage of battery 123 equals 350 volts.

The operation of the circuit will be more fully understood by yreferringto the diagram of Fig. 2 which greatly exaggerate-s the rapidity withwhich changes in the fork frequency occur. In ythis diagram, the( curlrent applied to the fork heater 69 is plotted against time in seconds.From zero to four from, the vcurrent supply at one-second ini" tervals.'When the fork 84 begins to vibrate too slowly, the synchronous motor108 slows down,'and, after the heater 69 hasbeen disconnected from thecurrent supply (as after the four-secondnterval) it is not againconnected to the current supply until a longer time than one second. Theelectric clock 110, however, is not affected by the frequency of thetuning fork 84 and continues to disconnect the current from the forkheater 69 at two second intervals. The current supply is accordinglydisconnected from the heater 69 at the six-second interval. It will benoted from the diagram that, as a result, less heat is applied to thefork 84 than when it is vibrating at the proper frequenc Accordingly,the tuning fork 84 wil be cooled slightly and kits frequency willincrease. In the diagram, the fork frequency begins to increase afterthe ten-second interval. After the twelve-second interval, the fork 84begins to vibrate too rapidly, and the synchronous motor 108 speeds up.This results in heat being applied to the fork 84 an instant sooner than1t would be'if the forkwere vibrating at the 5000-cycle frequency. lThetemperature ofthe fork 84 is, accordingly, increased and its frequencyis changed the desired amount. It will be noted that, at thesixteen-second interval, the fork 84 is vibrating so rapidly that thesynchronous motor 108 connects the heater 69 to the current supply assoon as it is disconnected by the. electric clock 110. It is evidentthat, if the fork 84 vibrates still more rapidly, the synchronous-motorspeed will be so high that its contact 130 will connect the fork heater69 to the current supply ]'ust before the contacts of relay 139 areclosed by the electric clock 110 to disconnect the current supply fromthe heater. When this happens, less, instead of more, heat is applied tothe fork 84 than is applied when it runs at the proper frequency, andthe system will not correct the fork frequenc VIn such case, a manualadjustment must made to increase the fork temperature. Under ordinaryconditions, no such adjustment is necessary. In the 500G-cycle generatordescribed, the synchronous motor I cla-iin asmy invention:

1'.' A constant-frequency generator comprising a mechanical elementhavingv a nat ural period of vibration, means for vibrating said elementat its natural frequency, and means responsive to changes in thefrequency of the output of said generator for maintaining the frequencyof vibration of said element constant.

2. A constant-frequency generator coinprising a mechanical elementhavingI a natural period of vibration, means for vibrating said elementat its natural frequency, and means for applying heat to said element,said means being responsive to changes in the frequency of the output ofsaid generator for changing the amount of heat applied to said element.

8. A constantfrequency generator comprising a mechanical ele-nienthaving a natural period of vibration, means for vibrating said elementat its natural frequency, means for applying heat to said element atperiodic intervals, and ineans responsive to the frequency of vibrationof said element for controlling the time between said intervals.

4. A constant-frequency generator comprising a mechanical element havinga natural period of vibration, means for vibrating said element at itsnatural frequency, and means responsive to the frequency of vibration ofsaid element for applying heat thereto in increments having a magnitudedependent upon said frequency.

5. A constant-frequency generator coinprising a mechanical elementhaving a n at ural period of vibration, means for vibrating said elementat its natural frequency, means for heating said element, a source ofcurrent, means responsive to the frequency of said element forconnecting said source Vto said heating means and means fordisconnecting said source from said heating means at regular intervals.

6, A constantffrequency generator comprising amechanical element havinga natural period of vibration, means for driving said element at itsnatural frequency, means including an electric heating element, forheating said mechanical element, a source of current, means forconnecting said source to said heating element at intervals dependentupon the frequency of vibration of said element, and means fordisconnecting said source from said heating element at regularintervals.

7. A constant-frequency generator comprising a mechanical element havinga natural period of vibration, means for vibrating said .element at itsnatural freque- Jy, means, including an electric heating element, forheating said element, source of current, means for alternatelyconnecting and disconnecting said source and said heating G5- elementand 'means for making the time between said connection and disconnectiondependent upon the frequency of vibration of said element.

S. A constant-frequency generator eoniprising a mechanical elementhaving a natural period of vibration, means for vibrating said elementatits natural frequency, means, including an electric heating element, forheating said mechanical element, a source of current, means forconnecting said source to said heating element after said mechanicalelement has vibrated a predetermined number of cycles and means fordisconnecting said source from said heating element at intervalsindependent of the frequency of vibration of said mechanical element.

9. A constant-frequency generator comprising a mechanical element havinga natural period of vibration, means, including an electric heatingelement, for heating said mechanical element, a source of current,means, including a synchronous motor driven by said generator, forconnecting said source to said heating element and means, including anelectric clock, for disconnecting said source from said heating element.

l0. A constant-frequency generator comprising a mechanical elementhaving a natural period of vibration, means for vibrating said elementat its natural frequency, means responsive to the frequency of saidelement for heating it and means for making said heating meansineffectivev at fixed intervals.

1l. A constant-frequency generator comprising a mechanical elementhaving a natural period of vibration, means for vibrating said elementat its natural frequency, means for heating said element, means formaking said heating means ineffective at intervals spaced apart by apredetermined number of vibrations of said mechanical element and meansfor making said heating means ineffective at evenly spaced timeintervals.

12. A constant-frequency generator comprising a mechanical elementhaving a natural period of vibration, means for vibrating said elementat its natural frequency, means for heating said element, means formaking said heating means effective at intervals spaced apart by a pefiod of time proportional to alpredetermined number of vibrations ofsaid element, and means for making said heating means ineffective thesame number of times it is made effective and at regular intervals,independent of the frequency of said element.

13. A constant-frequency generator comprising a mechanical elementhaving a natural period of vibration, means for vibrating said elementat its natural frequency, means for heating said element, a polar relay,a plurality of condensers connected to said relay, means for chargingsaid' condensers, means for operating said relay and making said heatingmeans effective when one of said condensers is discharged and means foroperating said relay and making said heating means ineffective whenanother of said condensers is discharged.

14. A constant-frequency generator comprising a mechanical elementhavinga natural period of vibration, means for vibrating said element atits natural frequency, means for heating said element, a polar relayhaving an armature and two windings, each of said windings having. acondenser connected thereto, means for charging said condensers, meansfor making said heating means effective when current isv passed throughone relay winding, means for making said heating means ineffective whencurrent is passed through the second relay winding, means responsive tothe frequency of vibration of said element for discharging one of saidcondensers through said one relay winding, and means independent of thefrequency of said element for discharging the other condenser throughthe second relay winding at regular intervals.

15. A constant-frequency generator com-- prising a mechanical elementhaving a nat@ ural period of vibration, means for vibrating said elementat its natural frequency,l

heating means for heating said element, means for alternately makingsaid heating means effective and ineffective,y and means for making thetime between the instant'the heating means is made effective and theinstant it is made ineii'ective dependent upon the frequency ofvibration of said element.

In testimony whereof, I have hereuntosubscribed my name this 26th day'of February, 1930.

FRANK CONRAD

